I use the mountain-bike style of SPD shoes and find them very comfortable for walking. Before I retired I frequently wore them around the office all day unless we had a meeting where more formal attire was expected. And I have no issues at all wearing them when shopping and similar utility trips. The ones I use look like pretty normal sneakers with regular laces, so people don't usually recognize them as cycling shoes.
I did experience some issues with the cleats when hiking in them on sandy and rocky trails. The cleats are recessed which protects them on smooth, flat surfaces, but on rough rocks found on hiking trails the cleats do get some extra wear. So now I usually pack another pair of shoes when bicycling to a hiking trailhead.